Hydrocarbon chlorination and alkylation process

ABSTRACT

A METHOD OF REDUCING THE PRODUCTION OF POLYCHLOROHYDROCARBONS IN A HYDROCARBON CHLORINATION COMPRISING FORMING A SOLUTION OF THE HYDROCARBON WITH A NON-OLEFINIC APROTIC SOLVENT SUCH AS BENZENE, HALOBENZENES, BENZENES AND NAPHTHALENES HAVING ELECTRON DONATING SUBSTITUENTS AND CARBON DISULFIDE, AND PASSING CHLORINE INTO CONTACT WITH THE SOLUTION IN THE PRESECE OF AN INTIATOR IS DISCLOSED. THE RESULTING MONOCHLOROHYDROCARBONS ARE PARTICULARLY USEFUL FOR ALKYLATING AROMATIC HYDROCARBONS TO PREPARE DETERGENT ALKYLATES.

United States Patent 3,639,494 HYDROCARBON CHLORINATION AND ALKYLATION PROCESS Richard E. Crocker, Anaheim, Calif., assignor to Atlantic Richfield Company, Philadelphia, Pa. No Drawing. Filed Feb. 17, 1966, Ser. No. 528,108 Int. Cl. C07c 3/52 US. Cl. 260-671 B 9 Claims ABSTRACT OF THE DISCLOSURE A method for reducing the production of polychlorohydrocarbons in a hydrocarbon chlorination comprising forming a solution of the hydrocarbon with a non-olefinic aprotic solvent such as benzene, halobenzenes, benzenes and naphthalenes having electron donating substituents and carbon disulfide, and passing chlorine into contact with the solution in the presence of an initiator is disclosed. The resulting monochlorohydrocarbons are particularly useful for alkylating aromatic hydrocarbons to prepare detergent alkylates.

The present invention is directed to a hydrocarbon chlorination process and more particularly to a process for reducing the amount of polychloroalkanes which are produced in the chlorination of alkanes or cycloalkanes. The process of this invention is especially suitable for use in the preparation of biodegradable detergent alkylate wherein chloroalkanes having chain lengths of C to C are formed as a preliminary step. The term alkanes, as used herein, is intended to include cycloalkanes as well as linear or branched alkanes.

The preparation of detergent alkylate fractions having straight chain alkanes as the alkane group has become of considerable commercial importance because these straight chain alkylate fractions can be used in the preparation of sulfonate detergents which are readily degraded by microorganisms available in sewage plants and river waters. The most popular previous method for preparing detergent alkylate has involved the use of such materials as propylene tetramer which is heavily branched and when alkylated with benzene forms a product having excessive resistance to biodegradability. The increasing contamination of our streams or other water sources with non or difliculty degradable detergents has received much attention by State and Federal ofiicials and has caused much activity to be directed to the preparation of straight chain alkyl benzenes that can be sulfonated to provide a detergent having good cleansing properties as well as gOOd biodergradability characteristics which will enable the avoidance of contamination of water sources.

In the preparation of straight chain alkyl benzenes, particularly those in which the alkane chain length ranges from about C to C one of the most popular methods for preparing the detergent alkylate (straight chain alkyl benzenes) has been to chlorinate straight chain alkanes such as n-dodecane to provide an alkyl reactant which can be easily attached to the benzene nucleus. The general reactions are represented by the following formulae:

RH C12 RC1+ HCl RC1+ +HCl ICC In the preparation of the detergent alkylate, according to the above noted method, it frequently occurs that a troublesome amount of polychloroalkanes are produced along with the monochloroalkanes. These polychloroalkanes, when reacted with benzene, produce a heavy detergent alkylate which is unusable and results in a waste of materials and a consequent reduction in the economics of detergent alkylate production. The polychloroalkanes produce when reacted with benzene such undesirable materials as diphenyl dodecanes, alkylindans, and alkyltetralins.

We have now surprisingly discovered that the amount of polychloroalkanes produced as side products in the chlorination of alkanes can be appreciably reduced by conducting the chlorination of the alkanes in the presence of an appropriate solvent instead of the usual practice in which the chlorine and alkanes are directly reacted under neat chlorination conditions.

The solvents which can be employed in the present process are liquid non-olefinic, aprotic compounds having a high solubility perameter. Included among these solvents are benzene, naphthalene, halobenzenes, halonaphthalenes, benzenes and naphthalenes having an electron donating substituent such as alkyl benzenes, alkoxybenzenes, and carbon disulfide. The solubility perameter of the solvents should be above 8.5 and preferably above 9.15. Some solvents which are eifective in the present process and their solubility perameters are as follows:

Of the solvents which can be employed in the present process, benzene is the most useful when the chloroalkane is to be used in detergent alkylate production, since it is used in the subsequent alkylation step and can be passed conveniently into the alkylation reaction zone without any separation of the solvent being required.

The process of the present invention may be practiced in various ways depending, among other things, on the solvent used and the compatability of the solvent with the intended use of the monochloroalkane product. In general, a mixture of solvent and hydrocarbon are fed into a mixing zone where chlorine is added and mixed with the solvent and hydrocarbon. It may be desirable to do the mixing under non-reactive conditions. The mixture of solvent, alkane and chlorine, is then passed into a reaction zone and exposed to an initiator, i.e., actinic light or heat, which promotes the chlorination reaction. After the chlorination reaction has continued for the desired period of time, the resultant products are passed into a non-reactive zone where the HCl generated by the chlorination reaction is removed. At this point, the solvent may also be removed if desired. If the solvent is benzene and the chlorinated hydrocarbon is to be used in a detergent alkylate process, the benzene would be retained for alkylation with the chlorohydrocarbons which are produced. If such materials as carbon disulfide are used as the solvent in a detergent alkylate process, they may be removed before the alkylation step.

The ratio of solvent to paraflin required in order to inhibit the production of polychloroalkanes can vary over an extremely wide range but generally best results are obtained when the solvent to hydrocarbon mole ratio is about 0.5:1 to about 20: 1.

The reaction is a liquid phase free radical reaction and suitable initiators include actinic light, heat, a peroxide, or any other conventional free radical initiator. The amount of chlorine added is dependent upon the amount of chloroalkane which is desired. A continuous process is preferred for the chlorination reaction, and backmixing should be avoided when possible since it tends to cause the production of unnecessary amounts of polychloroalkanes. The unreacted alkanes from the chlorination reaction can be recovered and recycled.

The temperatures used in the chlorination process generally range from about to about 200 C. The preferred temperature range depends upon the objective, that is, on the rate of chlorination that is desired. Higher temperatures tend to increase the rate of chlorination. The temperature and pressure should be controlled so that the reaction takes place in the liquid phase. The use of a solvent will reduce the relative amount of undesirable materials which otherwise would be formed regardless of the temperature used, amount of chlorine passed into the alkane-solvent solution, or the time of reaction.

The following examples illustrate in more detail the features of the invention and some of the advantages derived therefrom, but it is to be understood that they are not limitative of the scope of the invention. For example, dodecane, because of its availability, was selected as the alkane to be used in the tests; however, a number of alkanes, including cycloalkanes, are also within the scope of this invention.

EXAMPLE I A blank test was run using no solvent in order that results obtained later using solvents could be compared therewith. In this experiment, 244 gms. of dodecane was placed in a flask and blown with nitrogen for about 5 minutes to remove any oxygen present. The flask was then subjected to U.V. light and 35.6 gms. of chlorine gas was added to the dodecane slowly while the temperature was maintained at between 17 and 24 C. by means of external cooling. The total time of the reaction was about minutes after which the reaction was stopped and the product blown with nitrogen and then analyzed. The results are shown in Table 1.

EXAMPLE II A mixture of 244 gms. of dodecane and 62.4 gms. of benzene as the solvent, giving a concentration of benzene of 2 molar and a benzene to dodecane mole ratio of 0.56: 1, was placed in a round bottom flask and was blown with nitrogen for about 5 minutes to remove any oxygen which would otherwise inhibit the reaction. A U.V. light was then turned on the flask and 35.6 gms. of chlorine gas was added to the dodecane-benzene solution slowly while the temperature was maintained at between 17 and 24 C. The total time of reaction was about 15 minutes after which the reaction was stopped and the product blown with nitrogen and then analyzed.

EXAMPLE III A mixture of 249.6 gms. of benzene and 84.2 gms. of dodecane (representing a mole ratio of benzene to dodecane of 6.5 l) was blown in a round bottom flask with nitrogen, and then U.V. light was turned on the flask. The chlorine (12.3 gms.) was added over a 9-minute period. The temperature during the chlorination reaction was maintained at 1823 C. After the reaction was stopped the product was blown with nitrogen for about 5 minutes, and then it was analyzed with the results appearing in Table 1.

EXAMPLE IV A round bottom flask was filled with 312 gms. of benzene and 33 gms. of dodecane giving a benzene to dodecane mole ratio of 20.6:1. With U.V. light as the initiator, 4.8 gms. of chlorine was reacted with this solution over a period of 6 minutes. Because of the small amount of parafiin used, no external cooling was necessary and the temperature remainded between 19 and 24 C. The analysis of the product after the benzene solvent had been stripped is shown in the table.

EXAMPLE V A round bottom flask was filled with 61 gms. of carbon disulfide as a solvent and 260 gms. of dodecane giving a mole ratio of carbon disulfide to dodecane of 0.52:1. The solution was then subjected to U.V. light and 38 gms. of chlorine was added. Cooling was used to control the tem perature within a range of 12 to 23 C. and the chlorine was added over a 22 minute time period. The reaction product was blown with nitrogen and the carbon disulfide was separated therefrom. An analysis of the reaction prod ucts absent from the solvent is shown in the table.

EXAMPLE VI A flask was filled with 119 gms. of dodecane and 303 gms. of carbon disulfide giving a carbon disulfide to dodecane mole ratio of 5.37:1 .Following the procedure of Example V, 17.6 gms. of chlorine was added. After the carbon disulfide had been stripped, the product was analyzed with the results shown in the table.

EXAMPLE VII A mixture of 216 gms. of dodecane and 131 gms. of lchloronaphthalene as the solvent, giving a concentration of l-chloronaphthalene of 2 molar and a l-chloronaphthalene to dodecane mole ratio of 0.633: 1, was placed in a round bottom flask and was blown with nitrogen for about 5 minutes to remove any oxygen which would otherwise inhibit the reaction. An U.V. light was then turned on the flask and 32 gms. of chlorine gas was added to the dodecane-benzene solution slowly while the temperature was maintained at between 19 and 21 C. The total time of reaction was about 15 minutes after which the reaction was stopped and the product blown with nigrlogen and then analyzed. The results are shown in the ta e.

The data provided in the table shows that significantly less polychloroalkanes are produced when the chlorination process is conducted in the presence of a solvent as compared to the result when the alkane is chlorinated under neat conditions. This data also shows the marked reduction in polychloroalkane content achieved as compared to the theoretically predicted amount based on statiscal data. The statistical data was obtained from calculations based on statistical analysis of a chlorination reaction assuming that (1) the rates of chlorination of alkane, monoch loroalkane, dichloroalkane, etc., are the same, and (2) that the reactivities with the hydrogen atoms in the alkanes, chloroalkanes, and dichloroalkanes, are the same.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit or scope thereof and, therefore, only those limitations should be imposed as are indicated in the appended claims.

Experiment 1 2 3 4 5 6 7 Solvent None Benzene Benzene Benzene CS2 CS2 l'chloronaphthalene Solvent concentration, molar 8 2 10 2 Mole ratio solvent to dodecane 0. 56:1 6. 5:1 20. 6:1 0.52:1 5. 37:1 0. 63:1 Analysis of product, GO area percent:

n-Dodecane 72. 9 72. 8 69. 0 65. 9 66. 9 68. 7 81.6 pri-Chlorododecane. 2. 9 2.1 0. 9 0.9 2.0 0. 7 2. 5 sec-Chlorododecanes 21. 5 23.0 28. 2 31.1 29. 4 27. 4 15. 4 Polychlorododecanes 2. 7 2. 1 1. 9 2. 1 1. 7 1. 2 0. 5 Percent polychlorododecanes of theory 66 51 36 32 27 21 28 Batch chlorinations made at C b Compared area percent poly C1012 with predicted percent poly C1C12 calculated from area percent conversion.

I claim:

1. A method for reducing the production of polychlorohydrocarbons in a hydrocarbon chlorination process which comprises: forming a solution of a hydrocarbon selected from the group consisting of alkanes and cycloalkanes and a non-olefinic aprotic solvent selected from the group consisting of halobenzenes, Xylenes, ethylbenzene, nitrobenzenes, alkoxybenzencs, naphthalene, halonaphthalones, and alkoxynaphthalenes and passing chlorine into contact With said solution in the presence of a free radical initiator to produce a predominantly monochlorohydrocarbon product.

2. The method of claim 1 wherein said solvent has a solubility perameter of above 8.5.

3. The method of claim 1 wherein said solvent is lchloronaphthalene.

4. The method of claim 1 wherein the mole ratio of said solvent to said hydrocarbon ranges from 0.25:1 to :1.

5. The method of claim 1 wherein said hydrocarbon is an alkane.

6. The method of claim 5 wherein said alkane has a carbon chain length of from 6 to 18.

7. In a method for preparing detergent alkylate Wherein a hydrocarbon selected from the group consisting of alkanes and cycloalkanes chlorinated in the presence of a free radical initiator and the resulting monochlorohydrocarbons are reacted with benzene to produce alkylbenzene, the improvement which comprises: chlorinating said hydrocarbons in the presence of a non-olefinic aprotic type solvent selected from the group consisting of halobenzenes, Xylenes, ethylbenzene, nitrobenzenes, alkoxyben- Zenes, naphthalene, halonaphthalenes, and alkoxynaphthalenes to reduce the amount of polychlorohydrocarcarbons formed in said chlorination process.

8. A method for reducing the production of polychlorohydrocarbons in a hydrocarbon chlorination process which comprises: forming a solution of a hydrocarbon selected from the group consisting of alkanes and cycloalkanes and a non-olefinic aprotic solvent consisting essentially of carbon disulfide and passing chlorine into contact with said solution in the presence of a free radical initiator to produce a predominantly monochlorohydrocarbon product.

9. In a method for preparing detergent alkylate wherein a hydrocarbon selected from the group consisting of alkanes and cycloalkanes chlorinated in the presence of a free radical initiator and the resulting monochlorohydrocarbons are reacted with benzene to produce alkylbenzene, the improvement which comprises: chlorinating said hydrocarbons in the presence of a non-olefinic aprotic type solvent consisting essentially of carbon disulfide to reduce the amount of polychlorohydrocarbons formed in said chlorination process.

References Cited UNITED STATES PATENTS 3,019,175 1/1962 Haefner et a1. 204-163 3,378,476 4/1968 Hutson et al 204-163 CURTIS R. DAVIS, Primary Examiner US. Cl. X.R. 

